This application claims the priority of German Patent Application Serial No. 199 37 800.2, filed Aug. 10, 1999, the subject matter of which is incorporated herein by reference.
The present invention relates to an apparatus for condensation of steam.
It is known to provide air-cooled condensation plants with tube bundles of A-shaped or pitched-roof configuration which have proven to be cost-effective. The tube bundles are normally mounted in the form of a steel structure at an angle of 60xc2x0 to the upper platform of a substructure. The distance of the platform from the ground is dependent from the intake of respectively necessary amounts of cooling air. The upper ends of the tube bundles are fluidly connected to a common steam distribution duct. The steam to be condensed is conducted into the tube bundles via the steam distribution duct and condensed in the mainly externally ribbed tubes of the tube bundles, whereby the air intake is intensified by installing a ventilating fan below a certain number of tube bundles approximately in the plane of the platform. Depending on the type of admission, the lower ends of the tube bundles are connected to condensate collection pipes or dephlegmator pipes. The surrounding zone in the area of a ventilating fan is also called ventilating field.
The tube bundles, which oftentimes have a width of approximately 2.5 meters and a length of inclination of several meters, are generally not designed in a self-supported manner. Therefore, it is necessary to provide each tube bundle with a support frame which normally includes two slanted posts interconnected to one another and braced with the opposing support frame by crossbars. The support frames must be designed sufficiently stable to absorb in addition to the weight of the tube bundles also the weights, at least proportionately, of the steam distribution ducts and the condensate collection pipes as well as withstand forces from wind, snow and earthquakes. In addition, there are the forces of crane tracks located below the steam distribution duct and provided for the assembly and disassembly of the ventilating fans (motor, transmission).
Since the tube bundles are exposed to varying thermal stress, the greatest static load resulting from the own bundle weight has to be introduced via additional carriers at a statically inopportune location, i.e., in the area of the ridge and approximately in the lower third of the support frame in order to ensure a free thermal expansion of the tube bundles in longitudinal direction as well as in transverse direction.
As a consequence of the afore-mentioned factors, the conventional steam condensation apparatus has to be designed at comparably great size and correspondingly great weight.
It would therefore be desirable and advantageous to provide an improved apparatus for steam condensation which obviates prior art shortcomings and is light in weight and easy to assemble.
According to one aspect of the present invention, an apparatus for the condensation of steam includes a substructure; a fan supported by the substructure; a plurality of self-supported tube bundles arranged in a roof-shaped manner in opposing relationship with respect to a vertical center longitudinal plane and mounted to the substructure above the fan, with each of the tube bundles having an upper tube plate and a lower tube plate; a steam distribution ducts fluidly connected to upper ends of the tube bundles, condensate collection pipes fluidly connected to the tube bundles and mounted to an underside of the lower tube plates; wherein the upper tube plates of opposite tube bundles so support one another as to allow a limited pivotal movement of the tube bundles; and wherein the condensate collection pipes are so disposed on the substructure as to be shiftable relative to the substructure in parallel relationship to the center longitudinal axis.
An essential feature of the present invention is the self-supporting characteristics of the tube bundles. Thus, in their pure form, the tube bundles can be used as heat exchanger and, at the same time, for the reduction of static loads. The self-supporting function of the tube bundles is such that they do not only support themselves but are also able to receive the weight of the steam distribution duct as well as the condensate collection pipes (dephlegmator pipes) and also withstand forces from wind, snow and earthquakes and, if necessary, crane path loads.
Another essential feature of the present invention is the interconnection of opposite tube bundles to allow limited pivoting movement, and the attachment of the condensate collection pipes to the underside of the lower tube plates while allowing a displacement of the condensate collection pipes on the substructure parallel to the longitudinal center plane of the apparatus.
As a consequence of the self-supported design of the tube bundles, the need for expensive support frames for the tube bundles can thus be completely eliminated. The process requires only the provision of comparably light partition walls at the end face of a ventilation field. Internal calculations have determined that the total weight per ventilation field to be supported by the substructure can be reduced by approximately 65%.
As the condensate collection pipes are located directly underneath the tube bundles, the dimension of the apparatus can be decreased while a same output can be maintained, so that size and weight of the substructure can be reduced.
The particular disposition of the condensate collection pipes upon the tube bundles enables also a significant reduction in height of the steam distribution duct and thus of the entire apparatus, thereby greatly increasing the field of application, when taking into account that oftentimes customers have only limited heights available for placement of such apparatuses. Because of the reduced installation height as well as the reduced width of the apparatus, a wind screen to surround the steam condensation apparatus can also be kept lower and the length of the steam distribution duct can be shortened on the ridge-side longitudinal area. As a result, the weight of these components and the trapezoidal sheet plane for a wind screen lining can be reduced. The reduced construction height in view of smaller component size and reduced structural steelwork weights, decreases also the stress from wind and earthquakes to which the entire apparatus may be exposed.
In view of the fact that no support frames for the tube bundles are required, the flow of cooling air about the tube bundles is no longer impaired. This further improves the efficiency of the apparatus according to the invention.
The direct attachment of the condensate collection pipes underneath the tube bundles eliminates the need for a connection between the lower tube plates and the separate condensate collection pipes, as required to date. This is also accompanied by a reduced weight as well as a simplified welding operation during manufacture. Furthermore, the condensate collection pipes are able to realize a seal of the tube bundles beneath the lower tube plates so that the need for cost-intensive sealing plates, as required to date, beneath the tube bundles for preventing a recirculation of cooling air is eliminated.
Advantageously, the tube bundles together with the condensate collection pipes can be pre-assembled by the manufacturer, thereby significantly reducing cost-intensive welding seams and modifications in the area of the lower tube plates of the tube bundles.
The limited pivotability of opposing tube bundles via their upper tube plates allows a simple, rapid and cost-efficient change of a bundle inclination, if such is, for example, desired for process reasons. Prior art apparatuses require a change of the entire roof frame geometry, while the apparatus according to the invention allows a change of the inclination of the tube bundles through a simple adaptation of the positioning of the condensate collection pipes to the substructure as well as suitable selection of the mutual support of the tube bundles via their upper tube plates.
According to another feature of the present invention, the connection of the upper tube plates of the tube bundles can be realized by angle brackets, which are suitably arranged in spaced-apart disposition in longitudinal direction of the apparatus. They can be screwed or welded to the upper tube plates. A modification of the inclination of the tube bundles requires only replacement of these angle brackets. Still, the angle brackets permit a limited, mostly thermally based swivel mobility.
According to another variation, the upper tube plates may be coupled by fishplates which are placed above and below the upper tube plates and bolted together. Also in this case, it is only necessary, to loosen the bolted connection in order to quickly and safely change the tube bundle inclination.
According to still another variation, the upper tube plates may be connected to each other by hinged joints. In this case, there is no need at all for a replacement in the event of a change inclination of the tube bundles is desired. These hinged joints are each bolted or welded to the tubular plates via support sheets.
According to still another variation, the upper tube plates may be coupled with each other through U-shaped sections which are reinforced by webs and fastened to the underside of the upper tubular plates as well as connected to each other via webs. The U-shaped sections can be bolted or welded to the upper tubular plates as well as to one another. They often serve to secure a support rail for a crane path.
According to another feature of the present invention, the steam distribution duct may have a round cross section and is formed with a breach in the lower circumferential area, i.e. a wall area of the steam distribution duct has been removed. Welded next to the open circumferential area of the steam distribution duct on either side are one ends of spacers which are arranged in parallel relationship and welded with their other ends to the upper tube plates, in particular, to longitudinal edges that face away from one another. This configuration also allows that all components can follow the swivel movements at inclinations of the tube bundles.
According to another feature of the present invention, the condensate collection pipes may have a rectangular cross-section and can be defined by the lower tube plates of the tube bundles, bottom sheets and side sheets. According to the number of the neighboring tube bundles, these condensate collection pipes can be easily welded together. The carrying capability of the condensate collection pipes as well as the retention of the cross section is ensured by exterior vertical ribs. This, however, may also be realized by a thickening of the wall of the side sheets.
As an alternative, the condensate collection pipes may also have a triangular cross section and may also be externally reinforced by vertical ribs, whereby the cross section of the condensate collection pipes narrows from the tube bundles in the direction of the substructure.
The condensate collection pipes may also have a round cross section, in which case they are open in an area confronting the tube bundles and spaced from the lower tube plates by parallel longitudinal webs arranged next to the open circumferential areas. Suitably, all components are welded together. The condensate collection pipes as well as the longitudinal webs are externally reinforced by ribs.
Suitably, the displaceable positioning of the relative to the substructure may be implemented by guiding the condensate collection pipes on slide rails: which are directly mounted to the substructure or mounted to the substructure via base supports. In this manner, the tube bundles can follow any changes in length and width based on thermal influences without constraints.
According to another feature of the present invention, the slide rails may have a rectangular cross section, and the base supports may be guided by high-polished stainless steel angles on the slide rails, with the angles having predetermined areas coated with a sliding layer of polytetrafluoroethylene. The angles are arranged directly underneath the condensate collection pipes or at the lower ends of the base supports, and have a vertical leg and a horizontal leg for overlapping the rectangular slide rails from the vertical longitudinal center plane of the apparatus. The sliding layers made of polytetrafluoroethylene can be provided spotwise on the surfaces confronting the legs of the angle. Of course, strip-like sliding layers are also conceivable.
Suitably, the base supports are secured to the slide rails by screw fasteners which allow a limited movement between the base supports and the slide rails. In this manner, detachment from the slide rails is prevented. The screw fasteners may also be used to fasten the slide rails to the substructure.
According to variation of a sliding support of the condensate collection pipes, the slide rails are detachably or permanently secured to the substructure and may have a U-shaped configuration and are upwardly open. The bottom and the insides of the slide rails may be coated at predetermined areas with a sliding layer of polytetrafluoroethylene. Secured below the condensate collection pipes or the base supports in detachable or permanent manner are slide blocks, in particular, slide blocks of stainless steel. An engagement of the slide blocks in the slide rails ensures a perfect support of the tube bundles in the area of the condensate collection pipes.
According to another feature of the present invention, a rolling-type bearing of the condensate collection pipes on the substructure is also conceivable. This type of bearing may be realized directly or via base supports. A variation provides that the condensate collection pipes roll on the substructure via rollers mounted to the support stands. Suitably, the rollers may be supported by stop members towards the outside of the apparatus to absorb expansion forces.
According to another feature of the present invention, the condensate collection pipes may be supported on the substructure via multiple ball bearings. These multiple ball bearings can be provided, respectively, in circumferential regions of the vertical webs of a T-shaped base rail, and are overlapped by the vertical legs of a U-shaped slide rail which is directly or indirectly connected to a condensate collection pipe.
Suitably, the base supports are formed by U-shaped sections extending in the direction of the condensate collection pipes, when the condensate collection pipes have a round cross section. The U-shaped sections bear hereby with their legs upon the condensate collection pipes in circumferential manner. In this way, an exact position of the condensate collection pipes with respect to the base supports can be realized depending on the inclination of the tube bundles.